Tremolo effect producing device

ABSTRACT

A tremolo or chorus effect can be obtained by a tremolo effect producing device which comprises a balanced modulator for modulating a signal having a specific frequency with a musical sound signal, a band-pass filter for obtaining a single-band signal of the output of the balanced modulator, a demodulating circuit for demodulating the single sideband signal employing a signal the frequency of which is shifted from the above-mentioned specific frequency by a predetermined quantity and a buffer amplifier which amplifies the above-mentioned sound signal in a buffering manner, output signal from the demodulating circuit and the output signal from the buffer amplifier being thereafter mixed together.

United States Patent 172] lnventor Yasuji Uchiyama [56] References CitedI 2 I] A l N {Eg'g UNITED STATES PATENTS 2,835,814 5/1958 Dorf 84/125 x[22] Filed June 9,1970 5 [45] Patented 10 1971 3,267,198 8/1966 Hurvitz84/].25 X {73] Assignee Nippon cakkiseizo Kabushikixaisha 3,516,3186/1970 Wayne 84/].25 X

Hamamatsu-shi, Japan Primary ExaminerDi F. Duggan [32] Priority June 27,1969 Assistant Examiner-Ulysses Weldon [33] Japan Al!0rney-Holman &Stern [31] 44/50,88l

ABSTRACT: A tremolo or chorus effect can be obtained by a tremolo effectproducing device which comprises a balanced modulator for modulating asignal having a specific frequency with a musical sound signal. aband-pass filter for obtaining a single-band signal of the output of thebalanced modulator, a [54] g fir g ggfigfig g DEVICE demodulatingcircuit for demodulating the single sideband g signal employing a signalthe frequency of which is shifted [521 11.8. CI 84/1.25, from theabove-mentioned specific frequency by a predeter- 84/1.24 mined quantityand a buffer amplifier which amplifies the [51] Int.Cl 1. 010]! 1/04above-mentioned sound signal in a buffering manner, output [50] Field ofSearch 84/101, signal from the demodulating circuit and the outputsignal 124, 1.25, 1.26 from the buffer amplifier being thereafter mixedtogether.

A2 BUFFER AMPLIFIER E S E TF Al M O A 3 BA A NCED BIND I I3 TONE swncrmro-a DEMOOULATING INTERMEDIALE souecz clRcuit m5 AMPUFER -ga l glrteFfiS clRcurr AMPLIFIER fs fez fs-Af Q5 5 E W KEYBO OSCILLATOR gg gfiwgtx PATENTEU AUG 1 0 I97:

SHEET 2 OF 2 FlGimfltg FIG .3(b) r FIG. 3(d) FIG. 3(

FIG.4()

-- FREQUENCY FIG. 4(b) TREMOLO EFFECT PRODUCING DEVICE BACKGROUND OF THEINVENTION This invention relates generally to a tremolo effect(inclusive ofchorus effect) producing device. and more particularly to atype of device for creating tremolo effect sounds, by varying not onlythe amplitude but also the frequency thereof, in a purely electricalmanner.

Heretofore, tremolo or chorus effect producing device wherein a soundsignal is simply amplitude modulated with a signal having a desiredwaveform and frequency, or the sound signal is converted into sound bymeans of a loudspeaker rotatable at a desired speed have been proposed.(Hereinafter, a sound modulated with a frequency of from 5 to 7 Hz. isreferred to as tremolo effect sound and that modulated with a frequencyof from 0.5 to 2 Hz. is referred to as "chorus effect sound") However,in the first mentioned type of device, since the sound signal is merelyamplitude modulated with a desired signal with the frequency thereofbeing left unchanged, the resultant sound if rather monotonous and nosatisfactory tremolo or chorus effect can be obtained. The second typeof device, on the other hand, is accompanied by the Doppler effect inits operation, and the frequency, phase relation, and the radiationdirection of the output musical sound can be varied. In addition, theamplitude of the output musical sound transmitted in one direction isvaried in the second type of device, can a wide spread sensation of thesound can also be obtained.

However, the mechanism and the driving system of the rotatableloudspeaker in the second device are excessively complicated, and theproduction cost thereof is much too high. Furthermore, there are muchpossibilities for introducing various noises such as windbreaking noise,and many other mechanical noises at the time of the rotation.

SUMMARY OF THE INVENTION Therefore, the primary object of the presentinvention is to provide a novel organization of a tremolo or choruseffect producing device wherein all of the above-described drawbacksofthe conventional devices can be eliminated.

Another object of the present invention is to provide a novel tremolo orchorus effect producing device which can produce a sound signal which isnot only amplitude modulated but also frequency modulated.

Still another object of the present invention is to provide a noveltremolo or chorus effect producing device which can operate in a purelyelectrical manner and is simple in organization and economical inproduction.

These and other objects of the present invention can be achieved by anovel organization ofa tremolo or chorus effect producing device whichcomprises a balanced modulator for modulating a signal of specificfrequency with a musical signal, a band-pass filter for passing a singlesideband of the output signal from the balanced modulator, ademodulating circuit which demodulates the single sideband signalemploying a signal the frequency of which is shifted from theabovementioned specific frequency by a predetermined value, and a bufferamplifier which amplifies the above-mentioned musical sound signal forisolating the preceding circuit from the sub sequent circuit, wherebythe output signal from the demodulating circuit and the output signalfrom the buffer amplifier can be mixed together for obtaining thetremolo or chorus effect on the musical sound.

In another aspect of the invention, a level-adjusting filter forlowering the level of a signal in the low frequency region is providedat the output side of the demodulator circuit in the above-mentionedtremolo effect producing device, whereby the output of thelevel-adjusting filter is mixed with the output signal from the bufferamplifier.

The nature, utility, and the principle of the invention will be moreclearly understood from the following detailed description withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. I is a block diagram showing an example of the tremolo effectproducing device according to the present invention;

FIG. 2 is a block diagram showing another example of the deviceaccording to the invention;

FIG. 3(a) through 3(h) are graphical representations respectivelyindicating frequency spectra of signals obtained from various parts ofthe devices shown in FIGS. 1 and 2; and

FIG. 4(a) and 4(b) are graphical representations of tunings, based onthe equal temperament, of an ordinal musical instrument and of anelectronic musical instrument embodying the present invention.

DETAILED DESCRIPTION OF INVENTION Referring now to FIG. 1 showing anexample of the tremolo or chorus effect producing device according tothe present invention, when one of the keys in the keyboard K isdepressed, asignal having a frequency fs (the signal comprises not onlya fundamental frequency but also harmonic components, thus constitutinga frequency band, but for convenience in explanation in thisspecification, the band is referred to as fs only) generated in a tonesource circuit S is passed through a switching circuit E to a tonefilter circuit TF, so that the tone color thereof is adjusted therein.The signal is then amplified in an amplifier circuit A1. It should benoticed that the output signal fs from the amplifier Al has a certainband width as shown in FIG. 3(a). The signal fs is then passed to abalanced modulator M wherein a frequencyfol (see FIG. 3(b)) from anoscillator 0 which is oscillating at a frequency of, for instance, 50kHz., is balance modulated so that frequenciesf01+ fs andfol-fs areincluded in the output signal (see FIG. 3(a)).

Of these two signals, the upper sidebandfol+fis only is taken outthrough a bandpass filter F(see FIG. 3(d)) and is supplied to ademodulating circuit D. At the demodulating circuit D, the signal offrequencies corresponding to the upper sideband is demodulated employinga frequency f02 which is generated from a demodulating oscillator 0 andthe value thereof is selected to be higher than the above mentioned fol(of 50 kHz.) by a frequency Af of, for instance, 6 Hz. so that morespecifically the frequency f02=f01+AF50 kHz+6 Hz. (as indicated in FIG.3(e)) Thus, a demodulated signal will have a frequencyfsAf(as indicatedin FIG. 3(1)).

When the signal having a frequency off.rAf is mixed with original signalfs from an amplifier Al and through a buffer amplifier A2, the mixedsignal will be a signal having the spectra offs (a full line a)plusfs-Af(a dotted line b) as shown in FIG. 3(g), wherein the signal fsand the signal fs-Afinterfere each other to produce phase changeresulting in the amplitude modulation and with the frequency modulationat a frequency Af. The mixed signal is then amplified in an amplifier A3and passed, through an expression circuit EX and another amplifier A4,to a loudspeaker SP. In this manner, the sound varied in both theamplitude and frequency can be obtained from the loudspeaker SP.

In the above description, the frequency difference Af is selected to bein a range from 5 to 7 Hz. for obtaining a tremolo effect and isselected to be in a range from 0.5 to 2 Hz. for obtaining a choruseffect sound. The signalsfs and fr- Af from the modulating circuit D aremixed in a condition wherein both of the signals are at the same levelor either one of the signals is slightly lower than the other.

Furthermore, although it has been described above in the example of thetremolo effect producing device according to the present invention thatan upper side band signal is taken out employing a band-pass filter F,and the demodulating frequency f02 is determined higher than themodulation frequency fol by Af, various combinations of frequencies asindicated in the following table can also be employed for the samepurpose.

Actual characterlzm- Lsticsof Output input range filter F, signal,signal lolkllz, Al,llz lilterF kHz. 112.

[a 50 -ti My. 50 60 [-6 Lt 5o -fi ul-fr 40-50 fs-l-G [a 50 --'l HF-fa5060 f8+6 fr- 50 t3 folfs 40-50 fsti in FIG. 2, there is shown anotherexample of the present invention wherein a level-adjusting filter F, isfurther provided at the output side of the demodulator circuit D of FIG.1, and the signal fs from an amplifying circuit A] and through a bufferamplifier A2 is applied to the output side of the filter F Thecharacteristic of the filter F is so selected that the level of theoutput signal from the demodulating circuit D (see FIG. 30)) is loweredat the low-tone portion of the signal. As a result, the spectrum of theoutput signal from the filter F will show a configuration as indicatedby a dotted line b in FIG. 3(h).

it should be noted that an advantageous tuning can also be obtained atthe time the tremolo effect sound is produced in accordance with thisinvention.

This feature will be more clearly apparent from FIGS. 4(a) and 4(b)showing various tunings based on the equal temperament. Curves a and bin FIG, 4(a) show pitch deviations in ordinary musical instruments suchas a piano and a wind instrument, respectively. It is known that thetunings of the ordinary musical instruments will be felt natural tohuman ears when the tunings are done in such a way that the pitch isdeviated higher in the treble range and lower inn the bass range.

In FlG.4(b), curve a shows the deviations of the output signals of thedemodulating circuit D from the standard equal temperament, and curve I)shows the deviations of the mixed signals, of the output signals fromthe demodulating circuit D and the output signals from the amplifier Al,from the standard equal temperament. However, these curves deviateexcessively from the standard temperament pitch at the bass region, andthis excessive deviation of the curve b can be compensated to a moderatecurve c when the level-adjusting filter F, is provided at the outputside of the demodulating circuit D. Thus, the tuning of the tremoloeffect sound may be brought nearer to those ofthe ordinary musicalinstruments The entire tremolo effect producing device according to thepresent invention of the constitution as described above is composedpurely of electrical components, whereby the device can easily becombined with a specific tone color lever in the musical instrument, andin a musical instrument of a type having multiple stages of keyboards,the device can also be combined with one of these keyboards.Furthermore, the device can be produced without requiring anyhigh-precision mechanical technique, so that it has various advantageousfeatures such as economy in production, compact size, a tuning to rendernatural sensations of instruments, and capability to produce tremolo orchorus effect accompanying amplitude and frequency variations in theoutput sounds.

lclaim:

l. A tremolo effect producing device comprising a balanced modulator formodulating a signal having a first frequency with a musical tone signal,a filter for passing one of the sidebands of the output from saidbalanced modulator, a demodulating circuit which demodulates said singlesideband signal employing a second frequency differing from said firstfrequency by a predetermined small quantity, and a buffer amplifierwhich amplifies said musical tone signal with a buffer action, whereby adesired musical tone accompanied with a tremolo effect is obtained whenthe output from said demodulating circuit is mixed with the output fromsaid buffer amplifier.

2. A tremolo effect producing device comprising a balanced modulator formodulating a signal having a first frequency with a musical tone signal,a filter for passing one of the sidebands of the output signal obtainedfrom said balanced modulator, a demodulator circuit which demodulatessaid single sideband signal employing a second frequency differing fromsaid first frequency adjusting filter inserted at the output side ofsaid demodulator circuit for reducing the signal level at a low-tone rane thereof, and a buffer amplifier which amplifies said musica tonesignal with a buffer action, whereby a desired musical tone accompaniedwith a tremolo effect is obtained when the output from saidlevel-adjusting filter is mixed with the output from said bufferamplifier.

1. A tremolo effect producing device comprising a balanced modulator formodulating a signal having a first frequency with a musical tone signal,a filter for passing one of the sidebands of the output from saidbalanced modulator, a demodulating circuit which demodulates said singlesideband signal employing a second frequency differing from said firstfrequency by a predetermined small quantity, and a buffer amplifierwhich amplifies said musical tone signal with a buffer action, whereby adesired musical tone accompanied with a tremolo effect is obtained whenthe output from said demodulating circuit is mixed with the output fromsaid buffer amplifier.
 2. A tremolo effect producing device comprising abalanced modulator for modulating a signal having a first frequency witha musical tone signal, a filter for passing one of the sidebands of theoutput signal obtained from said balanced modulator, a demodulatorcircuit which demodulates said single sideband signal employing a secondfrequency differing from said first frequency adjusting filter insertedat the output side of said demodulator circuit for reducing the signallevel at a low-tone range thereof, and a buffer amplifier whichamplifies said musical tone signal with a buffer action, whereby adesired musical tone accompanied with a tremolo effect is obtained whenthe output from said level-adjusting filter is mixed with the outputfrom said buffer amplifier.